Sunday, May 6, 2012

Thompson Falls Bighorn Sheep Herd Continues to Decline

Based on recent surveys, the bighorn sheep herd in the Thompson Falls area (between Missoula and Libby) continues to decline. FWP Biologist Bruce Sterling counted only 52 sheep on his annual flight this spring. This figure compares to 270 sheep counted in 2008. These numbers reflect the number of sheep observed in the survey, not the total number of sheep in the population. But the trend is alarming to Sterling, who attributes most of the decline to highway mortality.

During the 2008-2012 period, a total of 110 sheep (50 ewes, 60 rams) were killed by collisions. A total of 107 sheep were killed on Highway 200 and 3 were killed by trains.

“We have lost 50 breeding or potentially breeding females during this time frame when hunters have taken only five ewes on permits,” Sterling says.

Sterling says that the highway mortality problem has been ongoing for decades, but seems to be more serious in recent years, noting that five sheep were taken out in one collision a few weeks ago.

“Now that we are at a low population level for sheep, each mortality is more critical,” Sterling says. He points out that since 1985, 403 sheep have been killed on the highway and 58 sheep were killed by trains.

Sterling cites a number of steps that have been taken to reduce highway mortalities of sheep, but they have not been effective. Yellow flashing caution signs and reader boards have not been successful in convincing drivers to slow down and avoid collisions with sheep. He says that the problem will be discussed at a meeting coming up with the Montana Department of Transportation officials on May 10.

Bighorn sheep were native to the Thompson Falls area but were extirpated by overhunting and disease passed by domestic sheep. Bighorns were re-introduced in the mid 1950s.